The invention pertains to a device for positioning a unilaterally pivoted lever arm in three different stable positions with two solenoids.
Whereas positioning in two stable positions does not present any problems, there is a lack of electromechanical devices which in a simple manner are capable of positioning an element in three different stable positions. Among other applications, such devices are used in recording instruments with several recording traces in which one writing utensil must record several parameters.
In Hasler Review 7 (1974), No. 1, pages 7-23, E. Winkler describes "a new electronic speed and distance measuring system for railways". This article illustrates a strip recording which apart from the main recording shows several additional recordings. A separate writing utensil is used to obtain sets of two additional recordings. Each of these writing utensils possesses two accurately defined deflections, each of which is allocated to a function to be monitored.
German patent document No. 213 317 deals with a recording unit in which one pen arm can be positioned in either of two deflections with two solenoids. The central rest position when the solenoids are switched off is obtained with two springs whose opposing forces are exerted on the arm.
The writing utensil is therefore capable of drawing an additional trace in accordance with the above-mentioned literature passage. However, the device is designed in such a manner that the springs must possess identical characteristics and forces to adjust the central rest position. In general, this requires an adjustment device.
The purpose of this invention was to obtain an improved device for positioning a unilaterally pivoted lever arm in three different stable positions with two solenoids. One application of such a lever arm shall be used to carry a writing utensil in a compact strip recorder which will record closely adjacent a main function and several auxiliary functions.